Apparatus for reversing furnaces



March 26, 1946. p NlELSEN 2,397,365

APPARATUS FOR REVERSING FURNACES Filed June 18, 1943 2 Sheets-Sheet 1 Fig.1. 4

INVENTOR lV/ELSEN; flQiL/Z March 26, 1946. N|EL$EN 2,397,365

APPARATUS FOR REVERSING FURNACES Filed June 18, 1945 2 Sheets$heet 2 fig. 5'. fig. 4

Patented Mar. 26, 1946 APPARATUS FOR REVERSING FURNACES Peer D. Nielsen, Lorain, Ohio, asslgnor to National Tube Company, a. corporation of New Jersey Application June 18, 1943, Serial No. 491,396

7' Claims.

This invention relates to apparatus for reversing a furnace of the regenerative type. In these furnaces air passes through regenerators where it is preheated and conducted to the fuel burners where it combines with the fuel to supply heat to the furnace. The burned gas passes out of the furnace on the opposite side thereof and through other regenerators where the heat from the waste gas is absorbed by the refractories in the regenerators, After an interval of time the direction of firing is reversed by shutting off the flow of iuel to the active burners and reversing the flow of air through the regenerators. A valve reversal system shuts off the how of air to the first men= tioned regenerators and initiates flow of air to the second named regenerators. At the same time how of the waste gas is reversed. In order to keep combustion conditions within the furnace con stant, these furnaces are often supplied with furnace pressure control systems. When fuel flow to the furnace is shut oi, the furnace pressure diminishes and the pressure regulating damper starts to close to increase pressure to the value for which the regulating system is set. Momentarily in the reversing cycle of the air and flue gas dampers, both waste gas dampers are partially open, thus exhausting the furnace system from oath ends and the pressure within the furnace proper is greatly diminished. causes the pressure control system to further close the pres sure regulating damper in an efiort to maintain control pressure on the furnace. Since such pressure control systemshave a tendency to over travel the control point,the pressure control damperat this time is practically closed. immediately following the complete reversal of the reversing dampers, the flow of waste gas from the furnace is necessarily completely reversed and the dis turbance caused by the reversal oi flow builds up a very high pressure in the furnace proper, thus causing the pressure control system to move the pressure control damper to a wide open position in an attempt to establish the desired control pressure. Application of fuel to the :Zurnace is impossible until furnace pressure diminishes to a suitable level. As the pressure control system tends to overtravel the control position, the dampers close more than is necessary for establishing the control pressure after having been in a wide open position and as application of fuel would result in a further increase of furnace pressure, its application must be delayed until the hunting of the furnace control valve ceases. Thus, it will be understood that the disturbances to furnace pressures attending furnace reversal is valves to and ill.

of such magnitude that the pressure control system cannot properly respond and the hunting" set up by the control system in an attempt to keep up with the rapidly and widely changing pressure conditions is detrimental to furnace operation.

It is an object of this invention to prevent hunting of the furnace pressure control during reversal of the furnace.

Another. object is to provide an interlock between the fuel supply and the furnace reversing system to prevent application of fuel to the wrong side of the furnace.

These and other objects will he more apparent after referring to the following specification and attached drawings, in which:

Figure 1 is a schematic layout of the furnace reversing control system of the invention;

Figure 2 is a side elevation of the timer;

Figure 3 is an end elevation;

Figure i is a plan view thereof; and

Figure 5 is a view of the control panel.

Referring more particularly to the drawings, thereference numeral 2 indicates a regenerative type furnace having burners i and 6 for supplying fuel to the furnace. The furnace shown is oil fired and the supply of oil to the burners is controlled by steam pressure operated valves 8 and Atomialng steam is supplied to the burners through pipes 32 and to. Supply oi steam to the burners and to the steam operated valves is con trolled by solenoid operated valves iii and i8. A double pole double throw switch to controls the energizing of the solenoids l6 and iii oi the A furnace damper reversal system 22 of common type is operated by means oi reversal motor 2d. a damper to in the due controls the furnace pressure, the position of the damper being varied by means of a piston moving in cylinder 32 which constitute part of the furnace pressure control systerri. The furnace pressure control system which is of a well known type has an impulse line at running from a point outside of the furnace near the arch thereof to one side of the diaphragm St. A sec- 0nd impulse pipe 38 runs from the inside of the furnace to the other side of the diaphragm 36. Oil is supplied to the pressure control system through pipe 60. The position of movable jet d2 determines whether oil is to be supplied to the cylinder 32 through pipes Ill or E6. The operation of the pressure control system is as follows:

If the pressure within the furnace is greater than the control pressure, the pressure in impulse line 38 will force the diaphragm 36 to the right,

oneness thus supplying oil to the pipe comes the piston to to move downworolly to open damper 26. iii the pressure in the iurnnce is less than the control pressure, oil he supplied to the ipe to closing the damper 26, thus the iurnnce pressure to that desired. Velveslli) end. in pipes 665 end 66 are operated by meens oi solenoids 38 end l'lil respectively, to control the flow of oil to the cylinder 82.

in the iurnece control system as shown in hip ure 1, air is tln'oueh regeneretors and tool is being odmitted through burners 6 while waste was is pessinc out through reeeneretors 50; When it is desired to reverse the furnace, switch 2i] is thrown to its neutral position. cle= energizes solenoid 06, thus closing sienna. velve iii. lfnen the steam been dissipoted. the sprint; closes velve 6, thus shutting oh? the flow oi oil to the burner l.

A second doulole pole double throw switch 58 is then thrown ircm the position shown to the ieit to moire contacts to and This closes the circult to reversing motor 26 through conductors L2, t l, 6%, to, contact 82, conductor l0, contest l2, conductors it and Li. At the some time solenoid it is energized by the current flowing from the conductor in through conductors i8 and co to conductor 68. This closes switch 82 causing the current to flow from conductor in through conductors I8, 86, and it, through coil iii to condoctor L1. This lights the lamp @ii to show that the reversal motor 2% is operating. Whencoii d8 of relay 92 is energized the armature 96 of the relay moves upwardly to mnlse contoct 9%?) closing the circuit to synchronous cloci: motor The synchronous clock motor rototes the com Mill through gear 602 and pinion not. On relay ormnture 84 is en arm Hi6 which is disposed to en gage the periphery of the com Milt. A notch fllil is cut in the com iilii and when engaged by the arm 106 causes the contacts to to be opened and contacts lid to be closed by the notion of the spring M2. With the arm Gilt positioned at any other part of the periphery or" the com ltd, contects 96 are held in in. closed position end contacts H in on open position. While the motor 93 is running, contacts remain closed and Eli solenoids to' and E58 sire deenergized, thus closing the valves d8 end end holding the demper it in. the position shown.

The motor it drives cums MG and M6 which open and close contacts M8 and i2 respectively. The cams are so constructed end rranged that contact '52 will be open one contest M8 closed when the damper reversol is completed. The opening of contact 712 opens the circuit to motor 24, thus stopping the motor. At the same time solenoid I6 is deenergized, opening switch 82 and causin the light 98 to go out. After waiting a few seconds to permit flow of gases through the furnace to complete reversal and to permit exhaust gases to escape from regenerator 54, the switch 20 is thrown to the right making contacts I20 and I22. This causes the current to flow through conductors L2 and 64, through solenoid I8, conductor I24, contact I20, conductor I26, contact 80 and conductors I28 and L1, thus energizing solenoid I8 and opening steam valve I8. This causes steam to fiow to the fuel valve I0 where it overcomes the force of spring I30, opening valve In and permitting oil to flow to the burners 6. Synchronous motor 98 and cam I00 are so constructed and arranged that the arm I06 falls into the notch I08 after suflicient time for pressure conditions in the furnace to become staloiiized. When the he not is in the comics, contoct tilt] is closed which causes current to flow in conductor L2 through contnct Mil, conductor i132, solenoids t8 and to, end conductors ti l end L1. The energizing oi solenoids t8 end to opens valves 38 and Eli, unlocking the pressure control end permitting norrnnl operation oi the control to resume.

Since the damper is locked in position durin reversal end until normel pressure conditions are established in the iurnece, it will be seen that the objectionable hunting during reversal is elimmeted. With switch iii! in its left hand position, air will flow through regenerators 5d and with the switch 58 inthis position it is impossible to energize solenoid it regnrdless oi the position of the switch 26). in like monncr with the switch thrown to the right, as shown in Figure 1, air will iiow through reeeneretors end it will be impossible to energize solenoid it) regardless of which way switch it is thrown. Thi provides an interlock between motor 2t and the valves it and it which prevents application of fuel to the wrong end of the furnace.

When it is again desired to reverse the furnace, switch 2c is thrown to a neutral position shutting oh the flow of steam to the burners, thereby stopping the flow of fuel oil and the switch 58 is thrown from its left hand position to the right hand position, closing the circuit to motor it through conductors L2, it, 56 and 6t, contact H38, conductor I133, contact M8, and conductors l4 and L1. The light @ll is lit, the timer set in operotion and the pressure control is locked in fixed position. When the reverse] of air flow is complctcd, contact M8 is open, stopping the motor 25, and the contact 112 is closed, thus preparing the control system for the next reversal. A push button switch M0 in conductor M2 is normally open but may be closed to operate motor 24 independently of the control system.

The switches 20 and 58, the light and timer 544 may be mounted on a. panel 6 in a convenient position. This enables the operator to determine the condition of the furnace at a glance. I

While one embodiment of the invention has been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the attached claims.

I claim:

1. in e. regenerative furnace having n motor for reversing the how of air and flue gas through the regenerators and automatic pressure control, the combination which includes means for shutting off the flow of fuel to the burners, means for actuating said motor to reverse the flow of air and flue gas and simultaneously lock the pressure control in fixed position, means for supplying fuel to the burners on that side of the furnace to which air is being supplied, and means for unlocking the pressure control a suflicient time interval after reversal for pressure conditions in the furnace to become stabilized.

2. In a regenerative furnace having a motor for reversing the flow of air and flue gas through the regenerators and automatic pressure control, the combination which includes means for shutting off the flow of fuel to the burners, means for actuating said motor to reverse the flow of air and due gas and simultaneously lock the pressure control in fixed position, means for supplying fuel to the burners on that side of the furnace to which air is being supplied, means for unlocking aso'ascs 3 the pressure control a suflicient time interval after reversal for pressure conditions in the furnace to become stabilized. and aninterlock between the fuel supply means and the reversal motor to prevent application of fuel to the wrong end of the furnace.

3. In a regenerative furnace having steam operated valves for supplying fuel to the burners, a motor for reversing the flow of air and flue gas through the regenerators and fluid operated means for controlling the furnace pressure, the combination which includes means for stopping the flow of steam to the burners and thereby stop flow of fuel to the burners, a timer, means for starting the reversing motor and simultaneously setting the timer in operation to lock the pressure control in fixed position, and means for supplying steam to the burners on that side of the furnace to which air is being supplied, said timer operating to unlock the pressure control a sufficient time interval after reversal forpressure conditions in the furnace to become stabilized.

4. In a regenerative furnace having steam operated valves for supplying fuel to the burners, a motor for reversing the flow of air and flue gas through the regenerators and fluid operated means for controlling the furnace pressure, the combination which includes means for stopping the flow of steam to the burners and thereby stop flow of fuel to the burners, a timer, means for starting the reversing motor and simultaneously setting the timer in operation to lock the pressure control in fixed position, means for supplying steam to the burners on that side of the fur- ,nace to which air is being supplied, said timer operating to unlock the pressure control a sufficient time interval after reversal for pressure conditions in the furnace to become stabilized, and an interlock between the fuel supply means and the reversal motor to prevent application of fuel to the wrong end of the furnace.

5. In a regenerative furnace having steam operated valves for supplying fuel to the burners, a motor for reversing the flow of air and flue gas through the regenerators and fluid operated means for controlling the furnace pressure, the combination which includes a solenoid operated steam valve for controlling flow of steam to the burners on one side of the furnace, a second solenoid operated steam valve for controlling flow of steam to the burners on the opposite side of the furnace, means for deenergizing the solenoids to close the valves and stop flow of steam to the fuel valves and thereby stop flow of fuel to the burners, a timer, an electric circuit, cams driven by said reversing motor, means for closing said electric circuit to start said reversing motor and set the timer in operation to thereby, stop the flow of fluid to the pressure control means, contacts in said circuit actuated by said a sufllcient time interval after reversal for pressure conditionsin the furnace .to become stabilized.

.6. In a regenerative furnace having steam opzerated valves for' supplying fuel to the burners,

a motor for reversing the flow of air and flue gas through the regenerators and fluid operated means for controlling the, furnace pressure, the combination which includes a solenoid operated steam valve for controlling flow of steam to the burners on one side of the furnace, a second solenoid operated steam valve for controlling flow, of steam to the burners on the opposite side of the furnace, a double pole double throw switch for controlling the energizingof said solenoids, a timer, an electric circuit, two cams driven by said reversing motor, two contacts in said circuit, each contact being actuated by one of said cams, the cams and contacts being so constructed and arranged that one contact is closed while the other is open, a double pole double throw switch in' said circuit, said last named switch being adapted to close said circuit to start said reversing motor and set the timer in operation to thereby stop the flow of fluid to the pressure control means, one of said contacts being broken when said air and flue gas reversal is completed to open said circuit to stop said reversing motor, said switches being constructed and arranged so that fuel can be supplied only to the burners on that side of the furnace to which air is being supplied.

7. In a regenerative furnace having steam operated valves for supplying fuel to the burners, a motor for reversing the flow of air and flue gas through the regenerators and fluid operated means for controlling the furnace pressure, the combination which includes a solenoid operated steam valve for controlling flow of steam to the burners on one side of the furnace, a second solenoid operated steam valve for controlling flow of steam to the burners on the opposite side of the furnace, a double pole double throw switch for controlling the energizing of said solenoids, a timer, an electric circuit, two cams driven by said reversing motor, two contacts in said circuit, each contact being actuated by one of said cams,

' the cams and contacts being so constructed and cams, one of said contacts being broken when arranged that one contact is closed while the other is open, a double pole doublethrow switch in said circuit, said last named switch being adapted to close saidcircuit to start said reversing motor and set the timer in operation to thereby stop the flow of fluid to the pressure control means, one of said contacts being broken when said air and flue gas reversal is completed to open said circuit to stop said reversing motor, said switches being constructed and arranged so that fuel can be supplied only to the burners on that side of the furnace to which air is being supplied, said timer being constructed and arranged to permit flow of fluid to the pressure control means a suflicient time interval after reversal for pressure conditions in the furnace to become stabilized.

PEER D. NIELSEN. 

